a) Field of the Invention
The present Invention relates to an optical system. Concretely, the present invention relates to an optical system which has a function to prevent an image from being blurred due to a camera shake, for example, a shake caused in particular at a time of photographing with a camera held by hands, and more specifically a finder for a photographing apparatus such as a digital camera, a film camera, a video camera or the like.
b) Description of the Prior Art
Known as conventional examples of finder optical system which has a camera shake correction function are those which are described in the following literatures:
Japanese Patent Kokai Application No. Hei 9-329820
Japanese Patent Kokai Application No. 2003-91027
Out of these conventional examples, a finder optical system which is described In Japanese Patent Kokai Application No. Hei 9-329820 has a composition shown in FIG. 32.
This optical system uses a camera shake correction lens component L disposed in the optical system. This camera shake correction lens component L is decentered in parallel with an optical axis of the finder optical system by a driving system A. Blurring of rays which are incident on the optical system from an object is corrected by decentering the lens component L as described above.
Furthermore, an optical system described in Japanese Patent No. 2003-91027 has a composition shown in FIGS. 33, 34 and 35. In FIGS. 33 and 34, a lens component L of an objective lens system is moved in a direction perpendicular to an optical axis. Moreover, an eyepiece component E is moved in a direction perpendicular to an optical axis in FIG. 35. A camera shake is corrected by moving the lens components as described above.
The above described conventional techniques adopt the lens components which has functions for correcting the camera shakes, or camera shake correction lens components. When the camera shake correction lens component is decentered, imaging performance is degraded by aberrations produced due to the decentering. Furthermore, distortion produced by the eccentricity makes an image asymmetrical with regard to an optical axis.
In addition, when the camera shake correction lens component has a large weight, this lens component constitutes a heavy burden which is imposed on an actuator which is used for moving the camera shake correction lens component.
When a camera shake detecting sensitivity is low, the camera shake correction lens component is moved for a long distance. When a camera shake sensitivity is high, in contrast, it is difficult to control a movement of the camera shake correction lens component.
A camera shake correction optical system has a lot of points which must be taken into consideration for its camera shake correction function as described above.